Consolidated Statements of Operations - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019		Sep. 30, 2018		Sep. 30, 2017
Income Statement [Abstract]
Revenues	$ 1,124	$ 1,058	$ 1,090	$ 1,203	$ 1,039	$ 958	$ 963	$ 1,045	$ 4,475		$ 4,005		$ 3,576
Costs and expenses:
Cost of revenue	(639)	(577)	(559)	(626)	(583)	(531)	(488)	(569)	(2,401)		(2,171)		(1,931)
Selling, general and administrative expenses	(408)	(372)	(354)	(376)	(398)	(343)	(337)	(333)	(1,510)	[1]	(1,411)	[1]	(1,222)	[1]
Amortization expense	(48)	(51)	(55)	(54)	(42)	(56)	(55)	(53)	(208)		(206)		(201)
Total costs and expenses	(1,095)	(1,000)	(968)	(1,056)	(1,023)	(930)	(880)	(955)	(4,119)		(3,788)		(3,354)
Operating income	29	58	122	147	16	28	83	90	356		217		222
Loss on extinguishment of debt	0	(4)	0	(3)	0	(7)	(23)	(1)	(7)		(31)		(35)
Interest expense, net	(34)	(36)	(36)	(36)	(33)	(33)	(36)	(36)	(142)		(138)		(149)
Other income (expense)	19	(16)	29	28	2	394	(6)	4	60		394		(40)
Income (loss) before income taxes	14	2	115	136	(15)	382	18	57	267		442		(2)
Income tax (expense) benefit	77	12	(48)	(50)	2	(61)	(19)	(52)	(9)		(130)		151
Net income	91	14	67	86	(13)	321	(1)	5	258		312		149
Less: Income attributable to noncontrolling interest	(1)	(1)	0	0	(1)	(1)	(2)	(1)	(2)		(5)		(6)
Net income attributable to Warner Music Group Corp.	$ 90	$ 13	$ 67	$ 86	$ (14)	$ 320	$ (3)	$ 4	$ 256		$ 307		$ 143

[1] (a) Includes depreciation expense of:$(61) $(55) $(50)